Several flow systems utilizes fluid flow rate control mechanisms for controlling the amount of fluid, which may be in gaseous (e.g., air) or liquid form passing through a flow channel. Flow control mechanisms might also be utilized to regulate flow rates in systems such as ventilators and respirators for maintaining a sufficient flow of breathable air or providing sufficient anesthetizing gas to a patient in preparation for surgery. Typically, flow rate control occurs through the utilization of control circuitry responsive to measurements obtained from fluid flow sensors. Such flow sensors can apparently measure the flow rate of the fluid by sampling the fluid along the wall of the flow channel.
In one implementation, flow sensors are positioned between upstream and downstream sides of the flow channel relative to the direction of the fluid flow to be measured. Airflow sensing devices generally have flow channels with constant up and downstream channel height. These upstream and downstream sides of the flow channel can create a difference in pressure and flow velocity of the fluid across the flow sensors, which leads to turbulent flow effects and flow eddies in the flow channel. The flow eddies can create instability in the fluid flow, which results in unstable output by the flow sensors. Further, the flow sensors may require additional flow restriction in the flow path of the flow channel, especially in a bypass of the flow channel, in order to limit the amount of fluid flow through the sensor and avoid output saturation.
The majority of prior flow sensors require precise and accurate alignment of the fluid flow path across sensing components of the flow sensors in order to avoid flow eddies in the flow channel. The precise and accurate alignment of the fluid flow path can increase the optimal performance of the flow sensors. Such approach requires extra precision can lead to extra design or set up time, and thus extra expensive, during the manufacturing of the flow sensors. Additionally, the flow channel may not produce uniform, laminarizing flow of the fluid due to non-uniformities in a cross-sectional area and position of the upstream and downstream channels in the flow channel.
In an effort to address the foregoing difficulties, it is believed that a need exists for an improved and inexpensive flow channel that reduces flow eddies and stabilizes a sensor output signal. It is believed that the improved flow channel disclosed herein can address these and other continuing needs.